I don't understand too much about dwell. A Holden (Isusu) Shuttle is a pasanger van 1982-1986? Is has a Isusu 4 cylinder motor much the same as a Gemini or Rodeo, 1.8 litre. It has NiponDenso stuff, and a magnetic distributor like a 2TGEU or any other Japanese NiponDenso thing. I think it is even the same distributor cap. The coil is a normal old oil one, used with a resister. I think it works good, dont think that is a problem. Not sure.
OK, I am running too rich down low, yes. How do I fix this? I think the venturi chokes are 32mm as standard. Jets are 125 mains, 150 airs, 55 slow jets. So I need smaller idle jets? Where do I get?